Electro-osmosis dehydrators use direct current (DC) power to form an electric field for removing water from sludge through electrophoresis and a voltage difference caused according to application of the DC power.
Such electrophoretic electro-osmosis dehydrators are disclosed in Korean Patent Application No. 10-2004-0007759 titled “ELECTRO-OSMOSIS DEHYDRATOR”; Korean Patent Application No. 10-2005-0009928, titled “PHASE CONTROL-TYPE ELECTRIC DEHYDRATOR”; Korean Patent Application No. 10-2007-0046494, titled “ELECTRO-OSMOSIS DEHYDRATOR”; Korean Patent Application No. 10-2008-0044901, titled “PHASE CONTROL-TYPE ELECTROPHORETIC ELECTRO-OSMOSIS DEHYDRATOR USING THREE-PHASE AC POWER”; Korean Patent Application No. 10-2010-0135183, titled “DRUM DEVICE OF ELECTROPHORETIC ELECTRO-OSMOSIS DEHYDRATOR HAVING IMPROVED ELECTRICAL CONDUCTIVITY, which was previously applied by the applicant of the present invention; Korean Patent Application No. 10-2010-0135185, titled “WASHING DEVICE OF ELECTROPHORETIC ELECTRO-OSMOSIS DEHYDRATOR; and Korean Patent Application No. 10-2010-0135188, titled “DIGITAL CONTROL CIRCUIT AND SYSTEM of PHASE CONTROL-TYPE ELECTROPHORETIC ELECTRO-OSMOSIS DEHYDRATOR USING THREE-PHASE AC POWER”. The electrophoretic electro-osmosis dehydrators include: a drum charged positively or negatively; a caterpillar spaced a certain distance from the drum, and entirely charged with polarity opposite to that of the drum; and a filtering fabric belt wound between the drum and the caterpillar to transfer and dehydrate sludge.
Constant pure DC voltage is applied across the drum and the caterpillar to form an electric field, and water surrounding sludge particles charged in the electric field is moved to an electrode charged with polarity opposite to that of the sludge particles, by electrophoresis and osmosis, thereby dehydrating sludge.
That is, since the surface of the sludge particles is negatively charged, when the electric field is applied to the sludge, the sludge particles are moved to a positive electrode, and water in a sludge particle layer is moved to a negative electrode, thereby facilitating the dehydration of the sludge.
Such electro-osmosis dehydrators require a certain gap between a positive electrode and a negative electrode, that is, between a drum and a caterpillar, and the efficiency of an electro-osmosis dehydrator depends on the gap between a positive electrode and a negative electrode. However, a filtering fabric disposed between the positive and negative electrodes degrades electrical conductivity therebetween, and increases the distance therebetween.
Moreover, the service life of such filtering fabrics are limited to about 6 months to about 9 months, and thus, a filtering fabric should be frequently replaced with a new one.